1. Field of the Invention
This invention relates to an image transfer device in which visualized images resulting from electrostatic latent images formed on an image bearing member being developed with developer are transferred to a continuous image transfer medium.
2. Description of the Prior Art
There is a technique whereby an electrophotographic apparatus for recording images by transferring toner images from an image bearing member to a continuous image transfer medium may be utilized to copy original images or utilized as the high-speed output device of an information process system such as electronic computer. In such technique, continuous paper such as fan-folded paper or rolled paper is commonly used as the continuous image transfer medium because of its ease of manipulation and its stability of conveyance.
In such apparatus, when toner images intermittently formed in dependance of the presence of recorded information are to be transferred to a continuous image transfer medium, it is necessary that the continuous image transfer medium be intermittently conveyed and, during non-transfer, the continuous image transfer medium must be separated from the image bearing member to prevent the transfer medium from being stained due to fog of the images.
Therefore, transfer of developed images to an image transfer medium has heretofore been accomplished by bringing the image transfer medium into contact with the developed images on the image bearing member with the aid of the mechanical action of an image transfer roller or bar or the like, imparting a charge to the transfer medium from the back side thereof, the charge being opposite in polarity to that of the toner forming the developed images, thereby causing the charge to attract the toner from the image bearing member to the surface of the image transfer medium. Thereafter, the image transfer medium has been separated from the image bearing member by the aforementioned mechanical action, whereafter the toner image transferred to the image transfer medium has been melted and fixed as by heating or pressure.
Heretofore, such contact with the transfer position and separation into the non-transfer position of the image transfer medium has been carried out mechanically by an image transfer roller or bar or the like, but the use of such mechanical means has encountered difficulties in adjustment of the distance between the image transfer roller or bar and the image bearing member and, in extreme cases, has injured the surface of the image bearing member or imparted unreasonable force to the continuous image transfer medium, thus having damaged such transfer medium. In addition, dust or like material on the continuous image transfer medium has sometimes been deposited on the image transfer roller or the like to hamper uniform image transfer or to cause other inconveniences.